Coolly received by critics on release, this dazzlingly directed and sharply edited thriller launched the Steven Spielberg phenomenon, spawned a shoal of increasingly sloppy sequels and turned “You're gonna need a bigger boat!” into a classic quote.

When I visited the location, I got the distinct impression that Martha’s Vineyard wants to be known more for its whaling history, its clapboard cottages and its literary heritage than for being the location for one of Hollywood’s greatest blockbusters.

That’s where the real island does differ from ‘Amity’. I suspect the savvy businessfolk of Amity would have gone on to promote the Xtreme Shark Attack Experience with their own animatronic Great White.

As a conservation area, the prestigious resort remains relatively unspoiled since its heyday as a whaling centre in the 19th century, and the movie’s locations remain unchanged.

The town centre, where Chief Brody (Roy Scheider) gets materials for the ‘Beach closed’ signs, is the junction of Water Street and Main Street, Edgartown, the one-time whaling port on the east coast (or 'down-island').

One of the primary ports for the whaling industry during the 19th Century, ships from all over the world docked at Edgartown's sheltered bay and ‘Captain's Homes’, suitably grand mansions with ornate top floor rooms (called 'widow's walks') overlooking the harbor, were built along Water Street.

At the end of Daggett Street, at the northern end of town, you’ll find the Ferry, to Chappaquiddick Island, which is where the Mayor (Murray Hamilton) has a quiet word with Brody about 'boating accidents'. The ferry takes pedestrians, bikes and up to three cars at a time. You may remember the name from the 'Chappaquiddick incident' in 1969, in which Mary Jo Kopechne died in dubious circumstances after Ted Kennedy's car plunged from a small bridge into the water.

West of the coast road north from Edgartown toward the popular resort of Oak Bluffs is Joseph A Sylvia State Beach, where the swimmers are panicked by the shark attack on the Kintner boy.

Alongside this beach stands the American Legion Memorial Bridge, under which the shark swims to the ‘safe’ inlet, Sengekontacket Pond, where Brody’s son is traumatised by the attack.

Across the island, toward the southwest tip, is the tiny fishing port of Menemsha. It was here, on North Road at the end of the harbour inlet between the General Store & Post Office and the Menemsha Galley restaurant, 515 North Road, that the workshed of old seadog Quint (Robert Shaw) was built.

A permanent building would have had to meet the island’s strict building regulations, so the structure was dismantled after filming and the area restored to its original state – including replacing any litter found on the site. Once again, it’s an empty lot.

The Orca’s scenes were filmed over 155 days at sea between Oak Bluffs and East Chop, under well-documented nightmare conditions.

The great shock moment, when Matt Hooper (Richard Dreyfuss) discovers the old fisherman’s nibbled head in the wrecked boat, was added as an afterthought. The ‘head’ shot was staged in the swimming pool of the movie’s editor, Verna Fields back in Los Angeles.